A common distinguishing feature of absorbent articles such as diapers, sanitary towels, incontinence pads, etc., is that they comprise elastic areas applied to different parts of the article. For example, it is usual for absorbent articles of the all-in-one type or pant type to comprise elastic areas in the waist section and in those areas which form the leg openings of the article when it is being worn. The function of the elastic of the waist section is, on the one hand, to hold the article in place around the waist and, on the other hand, to adapt the article to the size of the wearer's waist. The primary function of the elastic in the leg openings of the article is to seal against leakage of urine and/or faeces.
Other areas of an absorbent article can naturally also comprise elastic areas.
Various methods of elasticating absorbent articles are previously disclosed, one of the most commonly encountered methods involving the anchoring of extended elastic threads intermittently between two flexible layers of material, such as two nonwoven layers or one nonwoven layer and one plastic layer, or alternative arrangements. Once the anchoring has been effected, the loading on the extended elastic threads is relieved, causing the layers of material to interact with the elastic threads and to contract as a result of wrinkling.
Various methods for the intermittent anchoring of elastic threads exist. An example of a commonly encountered method of anchoring involves the intermittent application of adhesive to elastic threads immediately before the threads are applied between two flexible layers of material.
Intermittent anchoring can also be achieved by coating the elastic thread with a heat-activated adhesive material, the application of local heating through the layers of material and the elastic thread producing local anchoring of the elastic thread.
Another method for the intermittent anchoring of elastic threads between two layers of material involves coating one or both layers of material with intermittently arranged adhesive areas and positioning the extended elastic thread over these areas before the two layers of material are connected to one another.
It is also customary to apply continuous, parallel beads of adhesive to one of the layers of material and then to arrange elastic threads essentially perpendicular to the beads of adhesive. The beads of adhesive anchor the elastic threads intermittently, at the same time as they connect the two layers of material to one another.
One method for achieving discreet adhesive areas involves the application of a continuous and essentially sinusoidal bead of adhesive to one of the flexible layers of material, followed by the application of extended elastic threads along the bead of adhesive, as described in Patent Application EP 0,172,037 A1.
In Patent Application EP 0,510,455, intermittent anchoring of an elastic thread is achieved by coating the thread with a spiral-shaped bead of adhesive running around the thread in the longitudinal direction of the thread, whereby intermittent anchoring of the elastic thread is obtained.
An alternative method of elastic anchoring is described in U.S. Pat. No. 6,291,039, in which elastic, thread-shaped elements are anchored intermittently between two flexible layers of material without the use of adhesive. In conjunction with their anchoring, the elastic threads have been extended so that the diameter of the threads has been reduced. In this extended state, the layers of material that have been arranged on both sides of the elastic threads have then been connected to one another by means of a large number of connecting elements.
The connecting elements have been arranged in pairs very close to one another to either side of the elastic threads, whereby two connecting elements arranged in pairs form a connecting area.
This means that, when the extension of the elastic threads is reduced so that the threads are drawn together in the longitudinal direction, the diameter of the threads increases causing the threads to become wedged securely in the constricted passages or tunnels which the respective connecting area forms together with the layers of material.
The connecting elements appropriately consist of ultrasonically welded areas, as described in U.S. Pat. No. 6,291,039.
Alternatively, the constricted passages can be formed by heat-welding the layers of material together to either side of the extended elastic threads.
Other methods of producing the connecting elements are naturally also conceivable.
The application of patterns in the form of texts, images, symbols or the like to absorbent articles such as diapers, sanitary towels, incontinence pads, etc., is also previously disclosed. Combinations comprising at least two of the pattern forms are also encountered.
The texts and the symbols are preferably of an informative nature, for example in the form of an instruction for the wearer, a warning text or product information such as a size indication, for example.
The images are preferably in the form of decorative patterns, product information or instructions for the user.
Patterns in the form of trademarks and/or corporate logotypes are also commonly encountered.
The pattern is usually arranged on one of the layers which form the outside of the product when it is being worn, for example on the front or the rear end section of the product, on the fastening tabs or on one of the side panels. It is a particularly common occurrence for the pattern to be arranged on the outside of the product either at or close to the waist area of the product.
The pattern can relate to instructions in respect of how the product must be put on the wearer, the suitable size of the product for a certain weight of the wearer, or the like.
Patterns of this kind are usually positioned together with other types of pattern, such as a distinctive product mark, purely decorative patterns, positioning indicators for fastening tabs, for example, indicators intended to show which part of the product must be positioned facing forwards on the wearer, and so on.
The products thus comprises different types of pattern, some intended to inform the wearer of how to use the product, some only intended to make the product more visually attractive, and some intended to warn against incorrect use.
One familiar and commonly encountered method of applying a pattern to an absorbent article is to make use of an appropriate printing technology, whereby colour pigments are applied by means of a printing roller or the like to a layer of material appropriately on the outward-oriented surface of the article.
EP 604 729 is an example of a patent which addresses the problem of obtaining a printed pattern which exhibits improved resistance to wear after it has been applied to a nonwoven layer.
Also encountered is the arrangement of a pattern on an absorbent article by positioning a label containing a pattern on the article. The label in this case can be glued or welded securely to the article.
An alternative method for creating a pattern on a layer of material involves embossing the pattern onto the layer of material. The method requires the layer of material, to which the pattern is to be applied, to change its structure when it is subjected to embossing.
Comparatively bulky materials or laminates containing such comparatively bulky materials are particularly suitable for embossing by a combination of pressure and temperature in a so-called thermal embossing apparatus or in an ultrasonic apparatus, as described in U.S. Pat. No. 4,493,868. Examples of particularly suitable materials are thermally bonded nonwoven materials containing at least a certain proportion of thermoplastic material. When a comparatively bulky nonwoven material is subjected to local embossing, that is to say when it is subjected locally to a combination of pressure and temperature, the fibres are bonded together to form a surface exhibiting greater density. Adjacent areas that are not subjected to any embossing, on the other hand, retain their unbonded, bulkier structure, in which case the bonded surface forms a visible pattern in relation to the unbonded background structure.
Patterns can also be created by embossing on non-bulky materials, such as a plastic film, in which case patterns on the surface of the material can be created by embossing selected areas.
Patent Application US 2005/0228353 describes a method for creating a pattern on a plastic film.
A disadvantage associated with previously disclosed articles consisting, on the one hand, of an elastic area comprising thread-shaped elastic elements and, on the other hand, of a pattern, is that a separate machine component is required to create the pattern and another machine component is required to anchor the elastic threads.
Production machines comprising extra machine components tend to be more expensive with regard to their purchase and maintenance. The reliability of a production machine also reduces as the number of process stages increases, which usually manifests itself in a greater number of and longer production interruptions, higher levels of material waste and greater variations in the articles that are produced.
Absorbent articles comprising a printed pattern, of the kind described above, also suffer from the disadvantage that extra costs for colour pigments must be added to the other material costs.
Accordingly, there exists a need for an improved absorbent article, in which the process for the anchoring of elastic threads and for the creation of patterns can be simplified.
Further, there also exists a need for an improved absorbent article, in which the creation of patterns can be achieved with the reduced use, or without any use, of colour pigments.